Some computing devices such as mobile telephones are sold or leased on a prepaid/subscription basis, wherein a computing device herein is considered any device having a processor capable of executing instructions. In the future, more sophisticated computing devices, including general purpose personal computer systems, will be sold or leased on a prepaid/subscription basis. Attempts to modify such computer systems to avoid or reduce payment or will certainly be attempted.
As can be readily appreciated, software by itself is not a particularly reliable way to ensure that a computing device has not been modified to avoid or reduce payment. This is because programmers can change and/or patch the operating system code, install devices drivers and services, update components and so forth. For example, if software performed the payment status check, a malicious programmer (hacker) can patch a prepaid/subscription computer system to never check for payment status, or alternatively, to intercept the results of such a status check and convert a “not-paid” return status to a “paid” status.
As a result, various hardware-based ways to make a computer system or other computing device resilient to such modifications are being developed. For example, hardware can evaluate whether and when some certain set of code is executing, and act directly on the result. Defeating such hardware-based solutions would require physical actions such as making physical changes to the motherboard (e.g., cutting a power line to a chip), replacing a hardware chip or set of chips, and so forth. This can be made even more difficult through the use of glue and/or special packaging that make it harder to remove and replace a chip, and/or by requiring special communication (e.g., a heartbeat) with a chip that ensures it is still present.
Assuming that a computer system or other device may be made resistant to tampering, at least to the extent that doing so is not cost effective, another concern is what to do with respect to enforcement when an adverse issue such as unpaid status or tampering is detected. One solution would be to render the computing device completely unable to operate. However, this drastic solution has a major drawback in that such a computing device cannot be used at all, which means it cannot be used to renew an inadvertently-lapsed subscription for example. As such, enforcement that in some way limits the computer system's functionality is generally more desirable than totally disabling a system.
However, such an enforcement solution itself cannot be something that is easy to tamper with. Otherwise the enforcement solution that causes some adverse effect following the detection of a problem could be bypassed or modified to leave the computer system fully functional.